在类中分配函数指针会导致C ++中的值类型错误

Question

I've got this code within Entity.h, which is inherited by other classes. The idea is that in the inheriting classes can change the function either to avoid inheritance or to modify behavior.

public:
Entity(void)
{
    updateFunction = emptyFunction;
};
~Entity(void);
protected:
    void emptyFunction(){}
void (*updateFunction)();

The problem is that I get this error on compilation:

Error   2   error C2440: '=' : cannot convert from 'void (__cdecl Entity::* )(void)' to 'void (__cdecl *)(void)'    c:\documents and settings\administrator\my documents\visual studio 2010\projects\projectname\[projectname]\Entity.h 16  1   [projectname]

I've looked at tutorials all over again, it's been a while since I learned these stuff, but I cannot see some dissimilarity, what could be going wrong? IntelliSense unrelines the '=' symbol as the point of the mistake. I hope I didn't overlook anything.

Thanks a lot in advance!!

Answer 1

You need to decalre pointer function as:

class Entity{
public:
    Entity(void)
    {
        updateFunction = &Entity::emptyFunction;
        // ...
        (this->*updateFunction)(); //Call
    };
    ~Entity(void);
protected:
    void emptyFunction(){}
    void (Entity::*updateFunction)();
};

In fact updateFunction is not a normal function and it's a class member function.